The use of fingerprints for the identification of individual persons is of great importance in law enforcement and may become important in commercial transactions, such as credit card usage and the like. The use of fingerprints for identification of one individual out of a large number of people depends upon a description which enables speedy and reliable identification. The identification process generally involves matching an "inquiry copy" of a fingerprint set with a "file copy" of a fingerprint set by means of comparison of the respective classifier codes.
A fingerprint impression has several characteristics which have heretofore been used in classification systems. One of the principal characteristics is the fingerprint pattern which, in all cases, has an upper portion of concentric quasicircular ridges and a lower portion of a distinctive ridge format or pattern type. Many common pattern types have been given well known classical names such as plain whorl, plain loop, tented arch, etc. Another important characteristic which has been used for identification is the fine ridge structure of the fingerprint. The ridges include detailed features such as terminations or bifurcations of the ridge, called minutiae. These minutiea have been used as key features for purposes of visual identification.
In practice, fingerprint identification has been based upon the combination of pattern type, ridge information, and minutiae data. The well known Henry system is the predominant manual system used by law enforcement agencies and utilizes a code consisting of the pattern type for each of the ten fingers plus ridge count from certain fingers. In the Henry system a relatively small number of classifying characteristics are used and hence the total number of identifier codes that can be constrcted is too small to uniquely account for the millions of fingerprints in a comprehensive file. Consequently, a large number of file copies, as many as one thousand and more, each containing different sets of fingerprints must be filed under the same code number. This requires a large number of file copies to be searched manually in order to obtain an identification.
In recent years, various investigators have proposed mechanized classification systems for fingerprints to speed up the identification process. Some of these systems involve optical scanning of the fingerprint impression to produce electrical signals representative of the particular fingerprint and storing the data in an electronic memory for programmed retrieval and comparison. Such systems typically depend upon acquiring and storing information regarding the pattern type and the minutiae as the key elements for identification purposes.